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Isotopic Abundances and Atomic Weights: IUPAC Commission II.1 Today

  • Juris Meija

    Juris Meija <Juris.Meija@nrc-cnrc.gc.ca> is an Officer in Metrology at the National Research Council Canada, Ottawa and chair of IUPAC Commission II.1 on Isotopic Abundances and Atomic Weights (CIAAW).

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Published/Copyright: January 7, 2019
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Chemistry International
From the journal Chemistry International Volume 41 Issue 1

Abstract

It is hard to imagine IUPAC without the Periodic Table, and in turn, without atomic weights. As IUPAC celebrates its centennial, its oldest body, the Commission on Isotopic Abundances and Atomic Weights (CIAAW) turns 120. The parent Commission was formed in March 1899 and its inaugural task was to decide the atomic weight standard: should it be based on hydrogen or oxygen? Although the issue was settled in favor of oxygen, when the CIAAW formally joined the IUPAC in 1919, the question of the atomic weight scale was back for debate suggesting that many issues before this Commission transcend their scientific merit. In fact, many view the Periodic Table and changes therein as a part of larger cultural fabric of science so any changes are likely to be debated for a long time.

Atomic weights have a history that spans two centuries. Kepler and Newton taught us how to weigh planets and stars, and Dalton and with his contemporaries taught us how to weigh atoms. Atomic weights lay the foundations for many scientific measurements, many of which go largely unnoticed. For example, the 2007 definition of the kelvin (the SI unit of thermodynamic temperature) refers to a triple point of water with specific isotopic composition. Likewise, atomic weight of silicon played a special role in the recent efforts to redefine the kilogram and the mole. Most recently, the CIAAW was recognized in the International Vocabulary of Metrology, and its recommendations have been endorsed by the International Committee on Weights and Measures (of BIPM, the Bureau International des Poids et Mesures).

The CIAAW has changed significantly over the last several decades. One of the biggest impacts to its work has undoubtedly been the rise of digital communications. The CIAAW has recognized the value of disseminating its outcomes on the World Wide Web as early as 1995. Championed by Robert D. Loss, the first CIAAW website was setup in 1997 on servers at the Curtin University of Technology in Perth, Western Australia. In 2007, the ciaaw.org domain was registered, and the CIAAW website was redesigned to its current form in 2014. Recognizing that formal paper-based publication of standard reference data is a time-consuming process, recent revisions to the standard atomic weights have been first disseminated through iupac.org and ciaaw.org well before they appear in the pages of the IUPAC official journal Pure and Applied Chemistry. Note that atomic weights are summary outcomes derived from the isotope amount ratios. The CIAAW has not yet disseminated the isotope ratios in its publications but the online platform seems more appropriate than paper. In addition, online platform offers searchable data and interactive calculators.

The 2017 Atomic Weights Commission biennial meeting in the Netherlands (from left): Heiko Moossen, Tyler Coplen, Harro A.J. Meijer, Johanna Irrgeher (acting Secretary), Juris Meija (Chair), Shigekazu Yoneda, Philip J.H. Dunn, Jun Wang, Jochen Vogl, Tiping Ding, Norman Holden, Manfred Gröning, Xiang-Kun Zhu

The 2017 Atomic Weights Commission biennial meeting in the Netherlands (from left): Heiko Moossen, Tyler Coplen, Harro A.J. Meijer, Johanna Irrgeher (acting Secretary), Juris Meija (Chair), Shigekazu Yoneda, Philip J.H. Dunn, Jun Wang, Jochen Vogl, Tiping Ding, Norman Holden, Manfred Gröning, Xiang-Kun Zhu

The work of the CIAAW relies on the volunteers who are willing to engage in evaluation of isotope ratio measurements for the benefit of broader goals. Since 1902, the International Committee has been shaped by 120+ expert volunteers. A major change of the CIAAW in the recent decades has been the gradual increase in the youth of its members. In 1947, the average age of the CIAAW was at its peak—72—whereas today it is nearly at its lowest—just under 50. In addition, the gender diversity has improved significantly over the last decades. Marie Curie was the first woman elected member of the CIAAW in 1930 and of the eight women ever to serve to the CIAAW, half are from the last decade alone. These are all positive changes which will position the CIAAW to be more responsive in the upcoming years.

Although the issue that comes up most frequently is the name “weight,” which many find inappropriate, the CIAAW has plenty of technical issues at hand. Evaluation of atomic weight data is a complex endeavour. Here, one often faces mutually inconsistent measurement results which are separated in time by several decades. Given that scientific norms and standards evolve, it is not trivial to evaluate such results. Nearly one in ten revisions of the standard atomic weights, in fact, result in ‘less precise’ values. This is due to the fact that new measurements might reveal biases in the past measurements. The most recent example of this was the atomic weight of ytterbium with two available contemporary measurements more than ten standard uncertainties apart. Alternatively, standard atomic weights of other elements become ‘less precise’ as we learn the true extent of natural variations, as happened most recently for argon.

Whereas the 19th century chemists set out to determine the atomic-weight values with highest precision, culminating with the 1914 Nobel Prize in Chemistry for Theodore W. Richards, the 20th century was largely shaped by the quest to understand these values which lead to the discovery of isotopes and the realization that the atomic-weight values of many elements do vary in nature. Our drive to measure atomic weights and isotope ratios with ever-increasing precision is bound to reveal new phenomena.

About the author

Juris Meija

Juris Meija <> is an Officer in Metrology at the National Research Council Canada, Ottawa and chair of IUPAC Commission II.1 on Isotopic Abundances and Atomic Weights (CIAAW).

Published Online: 2019-01-07
Published in Print: 2019-01-01

©2019 IUPAC & De Gruyter. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. For more information, please visit: http://creativecommons.org/licenses/by-nc-nd/4.0/

Articles in the same Issue

  1. Masthead - Full issue pdf
  2. Introduction
  3. The International Year of the Periodic Table 2019
  4. Features
  5. IUPAC and the Periodic Table
  6. Criteria for New Element Discovery: Providing Assurance in a Field of Allure and Romance
  7. Looking Backwards and Forwards at the Development of the Periodic Table
  8. Isotopic Abundances and Atomic Weights: History of IUPAC Commission II.1 in the ­Service of Chemistry
  9. Isotopic Abundances and Atomic Weights: IUPAC Commission II.1 Today
  10. Isotopes Matter
  11. The New SI: The International System of Units is getting a Makeover
  12. IUPAC Wire
  13. Election of IUPAC Officers and Bureau Members—Call for Nominations
  14. Juris Meija Made the Top 40 Under 40
  15. C. Oliver Kappe is Awarded the 2018 IUPAC-ThalesNano Prize for Flow Chemistry
  16. OPCW to Further Enhance Contributions to United Nations’ Sustainable Development Goals
  17. 1001 Inventions: Journeys from Alchemy to Chemistry
  18. Stamps International
  19. Olympic Gold
  20. Project Place
  21. Critical Evaluation of Homogeneous Equilibrium and Solubility Constants of Gadolinium in Environmental and Biological-Relevant Conditions
  22. 23rd UNESCO/IUPAC Postgraduate Course in Polymer Science
  23. Guidance for the Compilation, Critical Evaluation and Dissemination of Chemical Data
  24. Making an imPACt
  25. IUPAC Periodic Table of the Elements and Isotopes (IPTEI) for the Education Community (IUPAC Technical Report)
  26. On the Discovery of New Elements (IUPAC/IUPAP Provisional Report)
  27. Bookworm
  28. Chemistry: Our Past, Present, and Future
  29. Conference Call
  30. Solution Chemistry
  31. Organometallic Chemistry and Challenges in CO2 Activation and Utilization
  32. Congreso Latino Americano de Química
  33. Energetic Materials
  34. Where 2B & Y
  35. Setting their Table: Women and the Periodic Table of Elements
  36. FAIR Publishing Guidelines for Spectral Data and Chemical Structures
  37. Croatian Meeting of Chemists and Chemical Engineers and 4th Vladimir Prelog Symposium
  38. IUPAC For Africa—Postgraduate Summer School on Green Chemistry
  39. In Honor of IUPAC’s 100th Anniversary
  40. Mark Your Calendar
https://doi.org/10.1515/ci-2019-0106

Articles in the same Issue

  1. Masthead - Full issue pdf
  2. Introduction
  3. The International Year of the Periodic Table 2019
  4. Features
  5. IUPAC and the Periodic Table
  6. Criteria for New Element Discovery: Providing Assurance in a Field of Allure and Romance
  7. Looking Backwards and Forwards at the Development of the Periodic Table
  8. Isotopic Abundances and Atomic Weights: History of IUPAC Commission II.1 in the ­Service of Chemistry
  9. Isotopic Abundances and Atomic Weights: IUPAC Commission II.1 Today
  10. Isotopes Matter
  11. The New SI: The International System of Units is getting a Makeover
  12. IUPAC Wire
  13. Election of IUPAC Officers and Bureau Members—Call for Nominations
  14. Juris Meija Made the Top 40 Under 40
  15. C. Oliver Kappe is Awarded the 2018 IUPAC-ThalesNano Prize for Flow Chemistry
  16. OPCW to Further Enhance Contributions to United Nations’ Sustainable Development Goals
  17. 1001 Inventions: Journeys from Alchemy to Chemistry
  18. Stamps International
  19. Olympic Gold
  20. Project Place
  21. Critical Evaluation of Homogeneous Equilibrium and Solubility Constants of Gadolinium in Environmental and Biological-Relevant Conditions
  22. 23rd UNESCO/IUPAC Postgraduate Course in Polymer Science
  23. Guidance for the Compilation, Critical Evaluation and Dissemination of Chemical Data
  24. Making an imPACt
  25. IUPAC Periodic Table of the Elements and Isotopes (IPTEI) for the Education Community (IUPAC Technical Report)
  26. On the Discovery of New Elements (IUPAC/IUPAP Provisional Report)
  27. Bookworm
  28. Chemistry: Our Past, Present, and Future
  29. Conference Call
  30. Solution Chemistry
  31. Organometallic Chemistry and Challenges in CO2 Activation and Utilization
  32. Congreso Latino Americano de Química
  33. Energetic Materials
  34. Where 2B & Y
  35. Setting their Table: Women and the Periodic Table of Elements
  36. FAIR Publishing Guidelines for Spectral Data and Chemical Structures
  37. Croatian Meeting of Chemists and Chemical Engineers and 4th Vladimir Prelog Symposium
  38. IUPAC For Africa—Postgraduate Summer School on Green Chemistry
  39. In Honor of IUPAC’s 100th Anniversary
  40. Mark Your Calendar
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